Exploration and Discovery History of the Cedar Wash Gold Project, Clover Mountains, Lincoln County, Nevada

Cedar Wash is a new early-stage gold prospect in an underexplored part of Nevada and is part of a growing number of Carlin-style gold deposits hosted by non-marine, shallow-water Tertiary carbonates in eastern Nevada and western Utah. Cedar
Wash was discovered in 2015 by the McEwen Mining exploration team. The project
is located on the eastern flank of the Clover Mountains, in Lincoln County, Nevada,
6–12 kilometers from the southeastern margin of the 36–18 Ma Indian Peak-Caliente
caldera complex. Previous exploration and mining activity in this area was limited to
historical iron and manganese prospecting.
In September 2015, McEwen Mining Inc (MUX), as part of a regional target-generation program, conducted a bulk leach extractable gold (BLEG) stream-sediment
survey. This survey was aimed at sampling streams draining mapped exposures of
the Eocene-to-Oligocene fluvial and lacustrine Claron Formation, the gold-host at the
Goldstrike Mine in Utah, 15–20 kilometers to the east. Positive BLEG results led to
the discovery of several gold-bearing jasperoid outcrops hosted by carbonate-bearing members of the Claron Formation. Subsequent mapping and sampling identified
three target areas, Goldstream, Cedar Wash and The Narrows, with outcropping altered and mineralized rocks. These target areas are aligned north-to-south over more
than 7 kilometers.
The upper part of the Claron Formation consists of lacustrine limestone interstratified with tuffs of the Needles Range Group (29–30 Ma) and is about 6 meters
thick. The lower Claron is generally a poorly-sorted sandstone, with a muddy calcareous matrix, and ranges from 25–60 meters thick. The Claron Formation lies unconformably on Mesozoic clastic sedimentary rocks and Paleozoic clastic and carbonate sedimentary rocks, which form the regional basement. Overlying the Claron is a
package of felsic-to-intermediate pyroclastic rocks of the Isom (0–160 meters thick)
and Leach Canyon (340 meters thick) Formations. No intrusive rocks have been identified.
Two forms of gold mineralization are found at Cedar Wash. Carlin-style mineralization occurs at the intersection of NNW- and WNW-trending structures in the carbonate-bearing subunits of the Claron, particularly at the upper contact with overlying volcanic rocks, and below the Needles Range tuff. Silicification and argillization
associated with iron-oxide minerals are the dominate forms of alteration. Carlin-type
pathfinder elements such as As, Hg, Sb and Tl, along with Ag, are elevated in altered
Claron. The second type is found in gold- and silver-bearing low-sulfidation epithermal quartz-calcite veins hosted by bleached and iron-stained volcanic rocks which
overlie the Claron Formation. Vein-hosted mineralization does not contain Carlintype pathfinder trace elements. The relationship between the two mineralization
types is not understood.
In the fall of 2016, a campaign of air-track drilling of 59 shallow holes was initiated in the three target areas. Near-surface gold mineralization was discovered in each of the three target areas, and a follow-up program of reverse-circulation (RC) drilling was planned. In early 2017, an RC drill was mobilized to the property to confirm
and expand mineralization discovered in the air-track drilling. Fifty-two RC holes
were drilled, resulting in multiple near-surface gold intersections, including 2 ppm
over 10.7 meters, 1.03 ppm over 16.7 meters, and 1.36 ppm over 16.7 meters. Zones of
mineralization containing Carlin-type geochemistry were identified at The Narrows
and Goldstream prospects, each with a strike length of 350 meters. Soil geochemical
surveys over portions of the project have identified gold, silver and trace-element
anomalies extending more than 2,000 meters beyond the drilled areas.
Key Words: gold, Carlin-style, early-stage, Tertiary, Claron Formation